May 9, 2014
Coronal Hole Squared
A coronal hole, almost square in its shape, is one of the most noticeable features on the Sun of late (May 5-7, 2014). A coronal hole is an area where high-speed solar wind streams into space. It appears dark in extreme ultraviolet light, as there is less material to emit in these wavelengths. Inside the coronal hole you can see bright loops where the hot plasma outlines little pieces of the solar magnetic field sticking above the surface. Because it is positioned so far south on the Sun, there is less chance that the solar wind stream will impact us here on Earth.
Credit: Solar Dynamics Observatory / NASA